I don't know whether anyone else has done this (forgive me if this is a commonly known thing) but I have coded all the FMC areas into Custom Data, so you can see the boundaries.

Those areas are already in SkyDemon, and you should see them in your Pilot Log before flight, and in the Radio tab during flight. If you tap on them in the radio tab the boundaries will briefly appear on the map.

They are indeed, but it’s a fiddle and temporary, and there is no prompt to do it. It was, though, a useful way to check my work!

The actual motivation for doing this was a meeting with a CAA Infringement Challenge Group, where we were talking about encouraging and reminding people to use listening squawks. The idea is to put them on the map, so people can see them and think “oh, yes, that would be a good idea“!

But, if people are happy with the way SkyDemon does it, perfect!

I prefer Timothy's solution.  I agree that the temporary nature of the SD functionality is fiddly and somewhat hidden.

Be careful what you wish for! 

On a recent flight from Blackpool to Hawarden I routed West of the Liverpool zone and intended to head South before joining at my base. As I crossed the Dee estuary I glanced down at my display and mistook the FMC upper figure of 3500' as being the base of the Liverpool CTA (3000'). Luckily I stated that I was 'climbing to 3300' to be given a polite reminder that the base of controlled airspace was below that. 

Nobody's fault but my own, but it does go to show that at times under a high workload and turbulence having too much information can easily trip you up.